Delivering multimedia content, such as audio and/or video, to terminal devices in digital format is becoming increasingly commonplace. Such content may include audio, video, and other content delivered over broadcast transmission media. Due to their nature, the bitrate of a multimedia (audio/video) stream may vary over time. Typical bit rates are 128-384 kilobits per second (kbps). Recent advances in video and audio compression accentuate this effect because relative bit rate variations are now greater than with older compression technologies.
A broadcast channel, such as a digital video broadcast handheld (DVB-H) has a fixed total capacity. The channel's exact capacity depends on the employed modulation parameters. For DVB-H, capacity is typically between 5 and 15 megabits per second (Mbps) for mobile and indoor reception. In DVB-H, this total bandwidth is divided into a number of timeslice channels that each have a static bit rate to facilitate mobility and handover.
For each multimedia stream, a certain amount of bandwidth is typically allocated to the corresponding broadcast channel (e.g., to the corresponding DVB-H timeslice). Ideally (but not necessary), a DVB-H timeslice channel contains only a single multimedia stream to lower power consumption in terminal devices.
Such bandwidth constraints can be enforced for a broadcast channel. This enforcement may involve buffering to flatten out bit rate variations. However, excessive buffering may introduce delays. Thus, an approach to ensure that delays do not become excessive involves allocating more broadcast channel bandwidth than the long term average of the stream bit rate. For DVB-H timeslice channels, this means that there will typically be leftover or spare bandwidth.
Bandwidth is a precious resource. Therefore, it is desirable to reduce the amount of wasted bandwidth.